A so-called retardation film to which various functions are imparted by controlling retardation of the film has been used for various applications.
For example, retardation films have been designed for the purpose of expanding a viewing angle depending upon mode of a different kind of liquid crystal cell in a liquid crystal display. Also, beside liquid crystal display devices, λ/4 plates having retardation of ¼ wavelength are being used as brightness enhancement films, pickups for an optical disc, or PS converters.
As methods for developing such retardation, there are known a method of stretching a polymer film, a method of coating a coating liquid containing a liquid crystalline compound on a substrate and aligning in a predetermined direction to thereby develop optical anisotropy, and the like. Of them, a method of controlling retardation using a liquid crystalline compound enables one to variously control retardation by properly selecting an alignment film, a liquid crystalline compound, an alignment-controlling agent for the liquid crystalline compound, process conditions for controlling alignment, and the like, can be applied widely, and can produce the product on a large scale with high speed (JP-A-2001-4837 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) and JP-A-2004-53841).
Also, as applications of the retardation plate, it has been proposed to apply it to organic electroluminescence devices, touch panels, 3D display devices, etc. with a structure wherein the plate is used at the front end position and not inside the device. However, conventional retardation plates have such problems as that they are liable to form scratches and are insufficient in strength, that they show a high reflectance when irradiated with outer light, that they have poor light fastness, and that stains are liable to deposit thereon and are difficult to remove. Thus, for use as a plate at the front end position, the plates have been required to be more improved.
In order to protect a liquid crystalline compound layer, a technique has been disclosed wherein a highly hard protective film is provided on the liquid crystalline compound layer (JP -A-2004-126534). However, it has been found that, since the liquid crystalline compound layer generally has optical anisotropy, merely providing a protective film having no optical anisotropy on the liquid crystalline compound layer causes a problem that light interference conditions so greatly differ depending upon viewing angle that rainbow-like unevenness or the like tends to occur.